Dynamics of classical spins on a lattice: Spin diffusion

Abstract

The transport of magnetization and of spin-spin energy are calculated numerically for classical gyromagnets, coupled by truncated dipole-dipole and nearest-neighbor exchange interactions, on sc, bcc, and fcc cubic lattices. For the exchange case the results agree with previous theory, and also agree with experiments on He3 for diffusion of magnetization (but not of spin-spin energy). For the case of dipole-dipole coupling, the results are in satisfactory agreement with previous theory for the angular average of the Zeeman diffusion, but disagree with experiment. Calculations are also presented for a lattice containing alternating moments of two different species: These show how the attenuation of diffusion by foreign spins (diffusion barrier) depends independently on the moment and gyromagnetic ratio of the foreign species. © 1992 The American Physical Society.